The first thing you must realize is that your motivations are unique and personal. You may train for social reasons, but not because your friend is making you. You may enjoy support of your parents, but can not compete for them. This is one of reasons children who are pushed too hard by imposed ambitions of overzealous parents often lose interest in a sport. The child has lost internal motivation to participate (fun) and generally does not stay involved long term. Make sure reasons you train are your reasons.

Secondly, define your reason. Be specific and write them down. Visualize payoff of your training. If one of your reasons is fitness, visualize yourself as fit and hardened individual you will become. Perhaps you have a specific personal goal in mind. Constantly remind yourself what that goal is, and how work out you are performing now will get you there.

2.Perform no more than 1-2 "break through" or high intensity interval work outs per week. Speed work puts more stress and body, and requires more recovery time. This type of work must performed prescriptively and carefully. Try to schedule your speed work or intervals work outs day prior to a rest or recovery day.

3.Train in 2-3 day cycles, with a rest or recovery work out in between cycles. This allows your body to adapt to stress of training. Some athletes will need more rest and less training, especially as intensity increases.

4.Change your shoes out frequently. A good rule of thumb is at least 3x per year for a high volume runner. You may want to write date you purchased your shoes in permanent ink on your shoes for reference. Buying shoes is expensive, but so is your insurance deductible.

5.Take supplements Chrondroitin Sulfate and Glucosamine. I don't recommend a lot of supplements, but this combination has shown promise in clinical studies, and in control groups of people suffering from knee pain. One works as an anti-inflammatory; other helps regenerate cartilage. I know of several orthopedic surgeons who are recommending supplement to their patients. It is definitely worth a try.

6.Increase your volume of endurance training by less than 10% per week. Bringing your mileage up too quickly is a sure fire way to promote injury. Your body adapts to stress (training), compensates for it, and builds or gets stronger. If you put too much stress on your body, it can't compensate and breaks down further instead of getting stronger.